Discussions on linux-scsi indicate that some SBC-2 devices may provide
some SBC-3 features and thus a SBC-3 BlockLimit page.
Supporting more than you claim is a transgression but a relatively minor
one, so lets turn a blind eye to it.
Supporting less than you claim is a serious transgression and will always
result in a harsh test failure.
Verify that the page length matches up with the size of the data in buffer.
Verify that page length is 0x3c if the device claims SBC-3, and 0x0c if not.
If the device claims SBC-3 and if it claims UNMAP support (LBPU)
then we check that both MAXIMUM UNMAP LBA COUNT and
MAXIMUM UNMAP BLOCK DESCRIPTOR COUNT looks sane.
Sane here means >0, <1M or 0xffffffff
If the device claims SBC-3 and if it does not claim UNMAP support (LBPU)
then we check that both MAXIMUM UNMAP LBA COUNT and
MAXIMUM UNMAP BLOCK DESCRIPTOR COUNT are both 0.
